The Roots type blower as shown in FIG. 1 is a two-shaft type blower. A housing 11 has an inner space 12 which is peculiar to the Roots type blower and an intake port 13 and a discharge port 14 which are communicated with the inner space 12. Two shafts 15 and 16 are rotatably disposed in the inner space 12 of the housing 11 by supports such as bearings 17, 18, 19 and 20 so that a given spacing, i.e., a gap, is provided between the shafts 15 and 16. The lower shaft 15 serves as a driving shaft.
The shafts 15 and 16 are rotated in opposite directions by synchronizing gears 21 and 22 which are disposed outside the housing 11. Rotors 23 and 24 are secured to the shafts 15 and 16, respectively, so that the rotors rotate in a predetermined phase with respect to each other. The rotors 23 and 24 are rotated in a spaced relationship with each other and with the inner wall of the housing 11 so that they do not interfere with each other.
When the rotors 23 and 24 are rotated, the blower intakes air from the intake port 13 and imparts kinematic energy to the air in the rotational directions of the rotors 23 and 24 within the inner space 12 of the housing 11. The blower then discharges the compressed air from the discharge port 14. Such a conventional Roots type blower has a disadvantage, among others, that is necessary to provide axial space in which to dispose the gears 21 and 22.